Do Diodes have a Wattage (or equivalent) rating?

[juz_ad]

Hello,

I hope this question makes sense…

The Resistors in the above diagram have a minimum Wattage rating based on the requirements of the circuit - do Diodes have a similar or equivalent rating?

e.g. If I know the maximum DC voltage at the input of this circuit will be +5V DC I can work out the Watts/Power rating for the Resistors…
…do Diodes have a similar rating or requirement?

I'm looking to take a through-hole circuit and reproduce it in the smallest SMT parts I can - but I'm not sure of all the implications of this as far as part ratings go.

Thanks.

 

[betwixt]

Yes they also have a power rating but it isn't calculated the same way as with resistors because a conducting diode has a fairly constant forward voltage drop. The power is calculated as (Vf * I) where Vf is the voltage drop and I is the current flowing through the diode.

Vf will vary according to the type of diode, For the 1N4148 it will typically be about 670mV at 5mA current.

Other factors can change the power loss but in your simple schematic you can ignore them. In this and your resistor circuit the components can be very small, there is hardly any power dissipation in any of the parts.

Brian.